This invention relates generally to control valves, and more particularly to chokes which serve to dissipate the energy of high pressure fluid, as for example fluid rising in a well.
Choke valves are commonly connected to the well annulus at the well surface to dissipate the energy of high pressure fluid, the latter commonly entraining small particles including drill cuttings loosened from the underground well formation. Such material can and does destructively erode the non-metallic seal carried by the choke valve due to exposure of the seal to the fluid flow when the valve is partly open, i.e. in fluid energy dissipating position. In this regard, when the valve is closed the seal is not exposed to abrasive fluid flow as the latter is stopped. There is need for a valve construction characterized by substantially reduced seal erosion and correspondingly increased life. Also, there is need for a choke valve construction further characterized by unusual simplicity and overall improved design, for compatibility with suddenly high well fluid pressure, as during a `kick` in the mud flow upwardly in the annulus between the well casing and drill pipe.